Tuesday, September 23, 2008

When Smoke Gets in Your Grapes

This summer, a series of wildfires swept through parts of California. Triggered by extremely dry conditions and dry lightning, the fires raged through parts of Northern California where grapes are grown. I was on the Mendocino/Sonoma border throughout this summer's fire season, and though were were tens of miles from the fires, we woke every morning to the smell of smoke in the air and that persisted all day. (photo of the fires in Mendocino by shellove)

At the time, I thought it was highly unlikely that the taste of the grapes would be affected by the smoke. It looks like I may be wrong.

In a story in the Santa Rosa Press Democrat, Kevin McCallum reports that growers are worrying because their fruit is giving off unusual odors. Scientists are currently analyzing the juice from Mendocino grapes to test for smoke taint. There is some concern that even low levels of smoke taint in the grapes will be amplified in the flavors during fermentation. While winemakers can use all kind of sophisticated filtering to get rid of some of the undesirable flavors out of the wine, at this point no one is clear about the extent of the problem or what--if anything--to do about it.

One of the questions I have is about how our famously subjective tastebuds will factor into this developing situation. Are some people going to taste smoke when they taste 2008 Mendocino and Anderson Valley wines? Will these tasters be in the majority? Or, like cork taint, will smoke be something that many tasters can't even detect in the wines?

It's too early to tell at this point. What I know for sure is that there's not much that will keep me away from continuing to buy North Coast and Mendocino favorites from vineyards like Navarro (which was only a mile and a half from some of the worst fires this summer). If anyone has any thoughts on this issue from a scientific, tastebud, or environmental perspective, please share them. I'm still kind of amazed that the grapes weren't able to flush any smoke that got into their tissues back out again over the course of the growing season.


john witherspoon said...

Hey Dr Debs
I found this study that exposed grapes to fire smoke post harvest. Here is the abstract, I can send you the PDF via email if you want but the link is blocked unless you have access to the journal.

Although smoke exposure has been associated with the development of smoke taint in grapes and subsequently in wine, to date there have been no studies that have demonstrated a direct link. In this study, postharvest smoke exposure of grapes was utilized to demonstrate that smoke significantly influences the chemical composition and sensory characteristics of wine and causes an apparent 'smoke taint'. Verdelho grapes were exposed to straw-derived smoke for 1 h and then fermented according to two different winemaking treatments. Control wines were made by fermenting unsmoked grapes. Sensory studies established a perceivable difference between smoked and unsmoked wines; smoked wines were described as exhibiting 'smoky', 'dirty', 'earthy', 'burnt' and 'smoked meat' characters. Quantitative analysis, by means of gas chromatography-mass spectrometry, identified guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-ethylphenol, eugenol, and furfural in each of the wines made from smoked grapes. However, these compounds were not detected in the unsmoked wines, and their origin is therefore attributed to the application of smoke. Increased ethanol concentrations and browning were also observed in wines made from grapes exposed to smoke. © 2007 American Chemical Society.

It will be very interesting to see how it pans out, but as you said, I won't be shying away from wines from this area anytime soon.

Dr. Debs said...

Interesting. I wonder if there is a difference between picked grapes and growing grapes--that maybe the same plant physiology that I thought would flush any smoke residue out actually circulates the smoke through the flesh and skin first.

One of the things I'm also still thinking about is how the trigger for anxiety was smell--the grapes smelled different. I often find my sense of smell is more acute than my taste, and this is what makes me wonder if the taste issue may not be moot.

Taster B said...

I've had some experience with smoke indoors and I can say this much: Smoke is very sticky. I wouldn't be surprised if a residue accumulated on the surface of the grapes and rain/water isn't enough to wash it completely off...

JR Moreau said...

I hope it doesn't affect the grapes.

I had a 2006 Cline Syrah this winter that tasted like liquid smoke was literally poured into the juice. I couldn't even drink it I disliked it so much. A little charcoal aroama and flavor is one thing, but drinking liquid carbon is another!

Jill said...

Maybe the smoke taint will lessen the need for new oak that can impart smokiness into the wines...